JPH06118192A - Apparatus and method for correcting injection of low-pressure cooling material for boiling water reactor - Google Patents

Abstract

PURPOSE: To obtain a safety device which responds to a failure by injecting a necessary amount of coolant into a circulating loop for a necessary period of time by actuating a low-pressure coolant injecting(LPCI) pump and opening injection valves in both LPCI areas when a loss of coolant accident happens. CONSTITUTION: When a state of emergency requiring suppression pool cooling occurs due to an accident, valves 91a and 91a supply a heat exchange loop function by means of a shut-off valve 108a and a fluid by-pass to a heat exchanger 114a from a suppression pool 84 and header 86. The fluid flows to a conduit 126a through an opened LPCI valve 120a. Then an LPCI valve 124a is closed so as to branch the cooling fluid to the pool 84. When a high- pressure state occurs in a containment, the pressure boundary of a containment mechanism is protected by using quenching or spraying. A cross-tie valve 172a is left opened and an orifice combination 118a cools a reactor core 80 while the recirdulating time and quantity of a water coolant are limited by means of an independent recirculating loop 56.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a loss of coolant accident in a nuclear reactor.

[0002]

Nuclear power plants have traditionally been designed to achieve long-term, safe, and reliable performance. To ensure safety, the plant incorporates devices and methods that show studied predictions of emergency situations.

Design approaches have examined theories or assumptions that may include design redundancy, for example as updated operating experience with nuclear power challenges new rules of performance. Thus, researchers in this field of electric power have developed improved analytical models for driving that show improved driving factor limits, and have determined higher levels of safety in view of changes in safety-related performance rules. Required to achieve.

Due to the inevitably long time intervals involved in developing or constructing new nuclear facilities, such efforts may include, for example, 10 years or more, and also many nuclear facilities currently in operation. In light of this, these researchers are generally required to meet the criteria of the new rules due to long-term facility modifications. Refurbishment procedures can be quite expensive as they require revised power sources, multiple valve replacements, etc.

The nuclear industry has developed numerous reactor types. One type that has found substantial use in the field is to generate steam for turbine drive within the core itself, referred to as a boiling water reactor (BWR). BWR reactor heating water serves not only as a working fluid, but also as a reaction moderator, and along with other parameters, its proper supply and application within the system is necessarily dependent on the Nuclear Regulatory Commission NRC. It was the subject of safety conditions or rulemaking by a governmental regulatory agency such as you.

[0006] Typically, the general structure of BWR nuclear power plants includes an upright reactor vessel incorporating a lower core structure with control rod drives underneath. Above the core, in sequence, is the steam separator assembly and the steam drying mechanism leading to the steam outlet. There is a shield wall around the core and a dry well outside it. A toroidal pressure suppression chamber (wetwell) is located below and surrounds the drywell.

In a more typical BWR installation, the water coolant is heated in the core such that it rises in the reactor vessel as a two-phase mixture of water and steam. This two-phase mixture then passes upward through the steam separator assembly and steam drying mechanism to enter the steam line leading to the turbine.

Following turbine drive, steam is condensed into water and returned to the reactor by the relatively large condensation and feed pumps of the water supply. The feedwater is a downcomer (down c
Enter the omer area.

Water in the downcomer region is shroud
Through a vertical recirculation pump that flows directly to a vertical injection pump located between the and the vessel wall (downcomer annulus)
Circulated through the core. In a typical manner, two separate recirculation loops with corresponding recirculation pumps are used for this recirculation function.

[Coolant loss accident (loss-of-coolant acci
In the case of some form of fracture or excursion, referred to as "dent LOCA)", the designer predicts that the relatively hot-high pressure water in the reactor will begin to be lost. Various safety devices and methods are then desired for both containment and thermal control of this LOCA.

Due to the latter thermal control, safety design terminates the core reaction at the loss of water moderators to eliminate the possibility of a nuclear accident, while generating heat or residual energy in the reactor. It will be appreciated that the momentum of ω remains high enough to require cooling control to avoid core melt, for example.

[0012] Generally, the amount of water in the containment vessel is for this reason contained in a more than adequate amount, for example in a supplement pool, or additionally in a condensation storage tank. In order to apply this water coolant for safety, various safety-related technologies or "emergency core c
ooling systems ECCS) ”was developed to comply with LOCA. For example, core spray
CS) equipment and low pressure coolant injection (low pressure coo)
lant injection LPCI) equipment has been developed in various configurations.

The LPCI system incorporates, for example, four pumps which are actuated by safety devices in the event of coolant loss. If the loss of coolant is of a sufficient range and the vessel pressure remains high, for example in the case of a small pipe break, an automatic safety device acts to depressurize the reactor vessel and To operate the relatively low pressure water supply pump. Since a recirculation device as described above is ideally constructed for this, it is generally
Used by LPCI equipment for water introduction, depending on CCS requirements.

[0014]

However, in the past safety design has recognized that the recirculation loop may be destroyed by a LOCA condition. Therefore, pumping water into the loop under such LOCA conditions may be ineffective.

Therefore, the LPCI device has a feature of recirculating loop selection called "loop selection logic" to avoid such situations. This safety control detects the broken recirculation loop and initiates the procedure of injecting water into the redundant, complete recirculation loop by activating the appropriate LPCI injection valve.

With experience with such LPCI loop selection features,
They have been found to be complex and difficult to test and maintain. By the conditions based on the latest rules,
The design must accommodate such occurrences as valve failure.

However, the procedure for retrofitting existing equipment to update them, in order to operate more effectively under the current regulations, is elaborate and quite expensive,
The execution involves work such as rewiring and pump connection work. Thus, researchers are seeking an approach that gives operators the opportunity to eliminate the conditions for loop selection logic management and associated costs, while further improving the reliability of LPCI devices.

[0018]

The present invention provides an injection loop modification that achieves effective insertion of water coolant within the recirculation loop of conventional boiling water reactors without resorting to complex loop selection logic. LPCI device and method.

The process recognizes that a fracture or rupture may have occurred within one of the recirculation loops and controls the rate and amount of simultaneous coolant injection into each recirculation loop.

With respect to the time for complete coolant injection,
And for a given volume of injected fluid, an analysis such as modeling the conditions of the LPCI is used to derive the flow rate of the injection and the LPCI method utilizes the flow rate to control hydraulic resistance in the coolant injection conduit. The amount of coolant required is determined and identified as controlled by the approach. Their hydraulic resistance can be carried out by means of conventional orifices, whose size and shape determine the desired flow rate, or by throttling of valves in the infusion conduit which achieve comparable results. By that method, the cross-tie conduits and associated cross-tie valves that would otherwise be used for recirculation loop selection for coolant injection are not actuated and simply remain open.

In this novel method and apparatus, the necessary LPCI modifications are achieved with minimal hardware concerns, rewiring or re-piping, and complex equipment and instruments otherwise required for loop selection. Don't rely on

In another aspect, the invention includes a core and normal operating pressures, first and second recirculation loops, respectively, including first and second circulation pumps and an operable discharge valve, a supplement pool water source. , A low pressure coolant injector for a reactor facility of the type having a boiling water reactor having a condensate storage tank and a safety device responsive to a loss of coolant accident to produce a safety output.

The apparatus includes first and second low pressure coolant injection pumps having a suction input and a discharge output and operable to pump water. A supply conduit arrangement is provided for connecting the suction inputs of the first and second low pressure coolant injection pumps in fluid flow communication with the suppression pool. First and second coolant injection conduits are provided, which are connected to respective discharge outputs of the first and second low pressure coolant injection pumps, and to respective first and second recirculation loops. First and second hydraulic resistance elements in the first and second coolant injection conduits, respectively, have been selected to provide a predetermined amount of water coolant to each of the first and second recirculation loops. A predetermined flow rate is provided to limit the flow of water coolant and the flow rate is selected to be effective in effecting emergency core cooling from a single coolant injection conduit. A controller is provided that is responsive to the safety output for operating the first and second low pressure coolant injection pumps.

In another aspect, the invention comprises an emergency core cooling water source, first and second independent recirculation loops for normally circulating water through the core for steam generation, and at least a predetermined amount of water coolant. Provided is a method for injecting low pressure cooling water into a boiling water reactor of a nuclear facility having a safety device responsive to a loss of coolant accident to generate a safety output to supply the reactor.

The method comprises the following steps.

Providing first and second water flow paths from the water coolant source to the first and second recirculation loops, respectively;

Providing a low pressure coolant injection pump operable to pump water from the water coolant source through the first and second water passages;

Providing a valve device operable from a closed state to an open state to create a flow in the first and second water channels;

Actuating the valve device in response to the safety output to permit simultaneous flow of water coolant in the first and second water passages;

Activating the low pressure coolant injection pump in response to the safety output;

A predetermined fluid selected to supply a predetermined amount of water coolant to the first and second independent recirculation loops, respectively, for the flow of water coolant in the first and second water channels. Limiting the flow rate, said flow rate being selected to be effective in effecting emergency cooling of the core from one of the water channels.

In another aspect, the invention includes first and second boiling water reactors having a core and normal operating pressure, first and second recirculation pumps, respectively, and first and second operable release valves. A low pressure coolant injector for a nuclear power plant of the type having two recirculation loops, a supplement pool water source, a condensate storage tank, and a safety device responsive to a loss of coolant accident to produce a safety output.

The device has first and second low pressure coolant injection pumps having suction and discharge outputs. A supply conduit arrangement is provided for connecting the suction inputs of the first and second low pressure coolant injection pumps in fluid flow communication with the suppression pool, and further the discharge output of the first and second low pressure coolant injection pumps. A cross tie conduit arrangement for selectively interconnecting the.

First and second coolant injection conduits are provided which are connected to the respective discharge outputs of the first and second low pressure coolant injection pumps and to the first and second recirculation loops, respectively.

First and second low pressure coolant injection valves are provided in the first and second coolant injection conduits, respectively, and are operable between closed and open directions.

Further, first and second respectively for limiting the flow of the water coolant to a predetermined fluid ratio selected to supply a predetermined amount of water coolant to the first and second recirculation loops. First and second hydraulic resistance devices are provided in the second coolant injection conduit, and the flow rates are selected to be effective in performing emergency core cooling from one coolant injection conduit.

A cross-tie valve device is provided in the cross-tie conduit, the valve device including first and second low pressure coolant through selected first and second coolant injection conduits to one of the first and second recirculation loops. It may operate between open and closed states to selectively direct the output of the infusion pump.

A controller is provided that is responsive to the safety output for the first and second low pressure coolant injection pumps.
Activating the first and second low pressure coolant injection valves and maintaining the cross tie valve device in the open position in the presence of a safety output.

Other objects of the invention will be in part apparent and in part later apparent.

Accordingly, the present invention comprises an apparatus and method having the structures, combinations of elements, arrangement of parts and steps exemplified in the following description.

For a fuller understanding of the nature and purpose of the present invention, reference should be made to the following detailed description taken in connection with the accompanying drawings.

[0042]

DETAILED DESCRIPTION A low pressure coolant injection system (LPCI) is necessarily implemented with several water retention elements based on the containment facility of a nuclear power plant.

With reference to FIG. 1, a containment facility or reactor building is designated generally by the numeral 10. Shown diagrammatically is an outer wall 12 having a floor 14.

In the structure 10, a boiling water reactor (BW)
R) Biological shield 1 surrounding the pressure vessel or reactor 20
There are eight components, the reactor pedestal 16. Drywell 22 is defined by a steel structure or wall 23. A toroidal pressure suppression chamber or wet well 24 surrounds the dry well 22.
The suppression chamber 24 is filled with approximately half water to define a pressure supplement pool 26, and a ventilator connects the drywell 22 to the supplement pool 26 of the wetwell 24.

Drywell / wetwell ventilation, as indicated by the main vents 28 and 29, extends from the drywell 22 to the containment chamber 24 and the respective aeration headers 30 and 31 contained within the air space of the containment chamber 24. Connected to and shown. Downcomer pipes 32 and 33 extend from respective headers 30 and 31 to terminate below the water surface of supplement pool 26.

The high-energy nuclear steam generation facility (Nu-clear steam Suppl) in the dry well 22 with extremely low possibility
y System NSSS) pipe failure, reactor water and / or steam is released to the drywell 22 atmosphere, indicating a Loss of Coolant Accident (LOCA). As a result of the increased drywell pressure, a mixture of drywell atmosphere, steam and water is forced into the water pool 26 in the containment chamber 24 via the venting device including the main vents 28 and 29.
The vapor condenses in the supplement pool 26, thereby limiting internal containment pressure. The non-condensable drywell atmosphere is transferred to and contained within the containment chamber.

The secondary containment or reactor building 10 further includes reactor 34 and 35 building rooms and refueled bed 3
Features such as 6 may be included. Chambers 34 and 35
In between are components such as spent fuel storage pools 37 and 38. Although not shown, the condensate storage tank (CS) is placed separately.
T).

The suppression pool 26, as mentioned above, provides a means for condensing the vapors released into the drywell area throughout the virtual LOCA; the decay heat is the residual heat removal RHR. ) A heat sink for the core insulation cooling system during the hot standby operation until it can be directly piped to the heat exchanger; a heat sink for venting the nuclear safety / relief valves; and an emergency core cooling system (Emergency core cooling
systems ECCS). The supplement pool also serves as a heat sink under normal operating conditions. Throughout the anticipated reactor transition period, steam is released downwards through the main steam safety / relief valve into the suppression pool, or it is released and condensed via a quench at the end of the discharge pipe. To be done.

Referring to FIG. 2, a highly schematic view of the recirculation elements associated with the reactor vessel 20 is provided. Vessel 20 includes a core 44 composed of a matrix array of fuel assemblies extending between core plate 46 and top guide 48.

The reactor core 44 is controlled by the control rods arranged in the assembly of the control rod guides 50. The control rod drive hydraulic lines and motors are accessible through the bottom of container 20 as generally indicated at 52. Mounted on the core 44 and a portion of the control rod guide assembly 50 is a cylindrical shroud 54 that operates to direct the circulation of water coolant within the vessel 20. At this point, the water is forced to flow downwards along the annulus (downcomer region) between shroud 54 and vessel 20, so that the water is somewhat continuously upwards through core 44. Directed to.

FIG. 2 additionally schematically illustrates a reactor water recirculation system implementing the LPCI modification of the present invention. The function of this reactor water recirculation device is to circulate a predetermined coolant and moderator in the core. When the apparatus consists of two loops or sections 56 and 57 that are external to the reactor vessel, the drywell 22 has pumps 58 and 60 for each loop inside. Each pump 58 and 6
0 is here for the sake of simplicity, respectively here the recirculation discharge valve 6
2 and 64 and respective suction or shutoff valves 66 and 68 are shown, but are configured in connection with a direct coupled water cooling motor with various valves.

In general, redundant recirculation loops 56 and 5
7 draws from the downward flow in the annulus or downcomer region between the core shroud 54 and the wall of the vessel 20,
A circulating flow is formed through the core 44. The flow in the core is about 1
/ 3 is obtained from vessel 20 through recirculation loops 56 and 57.

Within these loops, pumped at a higher pressure, dispensed through a manifold to which multiple pipes (not shown) are connected and returned to container 20. As a result, it is directed to a series of injection pumps, two of which are indicated schematically at 70 and 72.

When the flow is directed to the first stage of the injection pump, momentum exchange induces ambient water in the downcomer region to be drawn into the injection pump throat where the two flows mix, and the flow is the reactor. Lower plenum of container 20 (ple-na
m). The flow is then redirected upward through the core 44 for heat exchange. The water supply is added to the device through a perforated dispersion tube located above the downcomer annulus and joins the downward water stream.

The Low Pressure Coolant Injection Facility (LPCI) is part of the Residual Heat Removal Unit (RHR) and operates to inject water into the core through loops 56 and 57 in the case of LOCA. The coolant input approach is selected because the loop uniquely places the emergency coolant in the correct location within the container 20.

Due to such coolant loss conditions, normal operating pressure, for example 1,000 psi in the reactor vessel 20,
Partially released by manual excursion and through a vacuum. When this happens, the four LPCI pumps of the emergency core chiller are activated. These pumps can be used to additionally cool the water in the supplement pool 26 while being subjected to LPCI, as well as other RHR devices that operate (eg containment spray cooling, Suppression pool spray cooling and shut-off cooling).

However, in the case of signals that invoke the LPCI action, they are subjected to water injection in loops 56 and 57, as indicated by the respective input arrows 74 and 75. Thus, the coolant is the equipment 10
From the supplement pool 26 and the condensation storage tank (not shown), which are already available water sources by
Can be injected simultaneously at 4 and 75.

In the past, however, the correspondence of rules or conditions which had to be assumed that one of the loops 56 or 57 was broken was necessarily met. Therefore, the selective verbal logic was forced to select the loop that was viable for LPCI utilization. As mentioned above, this condition imposes the need for very complex control and water dispersion schemes.

Turning to FIG. 3, a schematic diagram is provided showing a split loop injection modification (SLIM) for a low pressure coolant injection (LPCI) device that is present in some existing nuclear power plants. In the figure, the reactor vessel 80 is a wall or structure 8
It is shown housed in the drywell formed by 2.

Shown additionally in the drywell region are recirculation loops 56 and 57. These loops are
Incorporating respective pumps 58 and 60, suction valves 66 and 68, and discharge valves 62 and 64 is shown as redundant, as before. Below and surrounding the drywell boundary 82 is an emergency core cooling system (ECCS) header 8 located in a shielded building.
6 is a toroidal-shaped supplement pool 84. Extending from the drywell wall 82 to the supplement pool 84 is a downcomer 88 that draws in liquid and / or vapor released by destruction.

Turning now to the Low Pressure Coolant Injection (LPCI) component, the suction inputs of the two pumps 90a and 91a, via lines 92a and 94a, E
It is connected to the CCS header 86 and the supplement pool 84.

Motor operated suction side valves 96a and 9
8a is connected to each input. Valves 96a and 98
a is normally open. In addition to being directed to ECCS header 86, it may be noted that line 94a
Is also coupled via line 100a to the condensation storage tank indicated by block 102.
The tank 102 is typically mounted some distance within the power plant facility and is an alternative source of water for the present LOCI.

The outputs of the pumps 90a and 91a pass through the heat exchanger bypass valve 108a and the respective lines 104a when the heat exchanger bypass valve 108a is opened.
And via 106a to line 110a.

The flow from conduit 110a is directed to conduit 116a and the flow is opened to LPCI valve 120a.
Through conduit 122a, but controlled by an orifice 118a or equivalent hydraulic resistance. By opening valve 124a and closing valves 128a and 132a, the cooling flow is conduit 13 to recirculation loop 56 downstream of discharge valve 62.
Injected via 6a. In such a case, the discharge valve 62 is closed. Injection and release valve 62 from line 136a
The location of the closure of the follows the assumption that a rupture occurs in the recirculation line.

In the non-accident state in which the suppression pool cooling is required, the valves 90a and 91a are closed valves 1.
08a serves to provide a heat exchange loop function and a fluid bypass from the suppression pool 84 and header 86 to heat exchanger 114a via conduit 112a. Upon cooling, the liquid then flows to conduit 110a.
The condition requiring pool cooling causes fluid to flow through line or conduit 110a to conduit 116a and through open LPCI injection valve 120a and to conduit 126a. Due to these normal conditions, the next consecutively placed LPCI injection valve 124a is supplemented via conduit 126a, cooling valve 128a, line 130a, consecutively coupled cooling valve 132a, and line 134a. It is closed to divert the cooling fluid to the cushion pool 84.

It may be experienced that a high pressure condition exists above the water in the supplement pool 84. This high pressure condition is caused by steam, and thus the pumps 90a and 91a can be used to perform a quenching action. In this respect, what we can understand is
A conduit 140a extends from conduit 110a to a first supplement pool injection valve 142a, the output of which is line 14
4a to the next consecutively connected suspension pool spray injection valve 146a, and via conduit 148a to the spray porous dispersion tube 150a.

A similar geometry of quenching or spraying may be used where high pressure conditions occur within the containment vessel inside wall 82. Such quenching serves to protect the pressure boundaries of the entire containment mechanism under accident conditions. Accordingly, conduit 110a extends to containment spray valve 154a. The output is then directed by line 156a to the next containment spray valve 158a in continuous connection, thus via line 160a and parallel line 162a to a pair of spray perforated dispersion tubes 164a and 166a.

The LPCI components described above in connection with recirculation loop 56 are implemented substantially symmetrically with respect to the corresponding components of recirculation loop 57. Such common components are identified by the suffix "a" in the description provided thus far for loop 56. Accordingly, components common to them with respect to recirculation loop 57 are identified in the figure by the same numbering and suffix "b".

In each case, double or redundant devices are ECCS header 86, supplement pool 84,
And the description provided in connection with the Condensation Storage Tank (CST) 102 and described above in connection with the recirculation loop 56 applies to corresponding components of the recirculation loop 52.

One additional feature of the LPCI device in the figure is the cross tie line indicated by conduit 170a, cross tie valve 172a, conduit 174, cross tie valve 172.
b and line 170b. This cross tie line was used in the apparatus described above for various purposes, including branching the flow pumped from one side of the redundant apparatus to the other. Without such control,
Or, in the absence of the inventive apparatus and method features, the pressurized water being injected follows the path of low resistance and exits the ruptured recirculation loop, while failing in the complete loop. The complexity associated with previous controllers is eliminated by the present invention.

With the device of the present invention, the cross tie valve 172
a and 172b remain open continuously. Correspondingly, the orientation combination 118a and 118b
Is selected to limit or limit the flow of water coolant to a flow rate that provides a predetermined amount of water coolant to each of the independent recirculation loops 56 and 57 at the same time. This flow rate is effective for implementing the emergency cooling of the core 80 within the required time constraint.

The flow rate established by the use of hydraulic resistance in each orifice 118a-118b is as follows: (a) core 8
It is based on knowledge of the amount of fluid required to perform zero required LPCI cooling, and (b) the time available to perform emergency cooling.

Analysis shows that a sufficient amount of this water is involved in this work. This is because the coolant passing through the ruptured one of the recirculation lines 56 or 57 is discharged to the dry well. That is, the coolant passes through the main vent hole and the drywell downcomer pipe, and the supplement pool 8
Flow to 4.

Accordingly, the correction technique is of great simplicity and is readily available for retrofitting existing BWR facilities. Only a minimum amount of hardware anxiety is introduced for refurbishment, no rewiring procedures or expensive re-piping procedures are required. In effect, the modified LPCI technology is of a somewhat passive nature. The improved technique is referred to as "Split Loop Injection Modification (SLIM)".

Referring to FIG. 4, an LPCISLIM logic diagram is shown. In the following discussion, the common components of the device previously identified by the suffix "a" or "b" are simply identified by the associated coding.

In the figure, block 1 and bracket 1
Reference numeral 90 indicates a safe output condition and a sensing parameter at which a corresponding initial signal is generated. At this point, a low water level may be detected within the reactor 80, as shown at logic diagram location 192. This condition can be obtained, or high drywell pressure can be detected, as shown at position 194. These conditions indicate detection of a Loss of Coolant Accident (LOCA). Upon their detection, the control logic then proceeds to position 200, as shown in respective lines 196 and 198. There, the standby diesel engine is started to energize the pump motors as well as the power source for the electric drive elements that operate to control these motors or the valves used in this device. This area of the logic diagram is shown identified in the block and bracket 202 to make available power to the valve and pump motors and to meet the "tolerance" criteria, the latter condition being shown to the reactor 80. Relatedly, it is a condition set when the required low pressures P1 and P2 are reduced or developed.

Following initiation of the power drawn by the diesel engine, then lines 204 and 206
At positions 208 and 210, respectively, to determine if power is available to one or more buses that power the valves as in the identified LPCI pumps 90, 91 and 120, 124, and 62, 64. Or a decision is made. Accordingly, as shown by line 212 and position 214, LPCI infusion pump 9
A decision or decision is made about the presence of power at 0, 91. At the same time, it is determined that power is available to the LPCI injection valves 120 and 124, as indicated by line 216 and position 218. In addition, line 22
A determination or decision is made as to whether power is available to the discharge valves 62 and 64 of the respective recirculation loops 56 and 57, as indicated by 0 and position 222.

Additional conditions are provided in connection with the condition shown at position 218 for powering LPCI injection valves 120 and 124. As indicated by lines 224, 226 and position 228, the pressure presented at the reactor 80 must drop below a predetermined lower pressure P1. The pressure is, for example, 300 ps
It can be in the range of i to 400 psi. In this regard, the injection valves 120 and 124 are allowed to operate only if there is a constant pressure differential between them.

Another permissible condition within the logic disclosed in block and bracket 202 is indicated at position 230 where a decision or decision is made as to whether the reactor pressure is below a pre-specified value P2. This value, P2, is less than or equal to the pressure value P1, and is, for example, about 200 psi. If the conditions are met, the logic remains on line 232.

The logic diagram then continues to the area indicated by the block and bracket 234 which provides pump and valve actuation. It can be further noted that logical diagrams can be vertically categorized. For example, block and bracket 236 shows the area for the initiation of LPCI pumps 90, 91, while block and bracket 238 shows the vertical area of the same figure associated with the opening of injection valves 120, 124, and block and bracket 240 respectively. Associated with closing the discharge valves 62, 64 of the recirculation loops 56 and 57 in FIG.

Therefore, it should be noted that the position 214
The LPCI pumps 90, 91 are ready for rated flow, as shown by line 242 and position 246, upon determining or determining the presence of power at pumps 90 and 91 as shown in FIG. This indicates that pump operation is at rated speed and is currently delivering flow at rated capacity. The control condition is that the condition of perfect flow is L
Require PCI devices to be met before they are estimated to be available for LOCA conditions.

Attention is now directed to the presence of power at the LPCI injection valves 120 and 124, and the matching of the pressure acceptance conditions as shown at position 228.
Due to the co-occurrence of these conditions as indicated by
Logic flow continues to identify the conditions under which the LPCI injection valves 120 and 124 are opened, as indicated by line 252 and position 254. Similarly, it is also necessary that the discharge valves 62, 64 be closed in the vertical region 240 as shown at position 256. This discharge valve closure for the recirculation loops 58 and 60 is made on the assumption that the break in the recirculation loop is on the suction side of these recirculation pumps. Thus, the injection of the LPCI device is pump 58,6.
0 discharge side, as well as the corresponding discharge valves 62, 64.

Finally, it is necessary that the conditions represented by positions 246, 254, and 256 in the figure occur together. This condition is indicated by the merge lines 258, 260 and 262.

It is contemplated that some changes may be made to the above apparatus and method without departing from the scope of the invention provided herein, such that it is encompassed above or annexed to. It is intended that all matter shown in the drawings be interpreted as illustrative and not in a limiting sense.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing one design of a reactor building;

FIG. 2 is a schematic diagram of a reactor vessel and two associated recirculation loops;

FIG. 3 is a schematic fluid flow diagram showing a low pressure coolant injection system incorporating features of the present invention; and

FIG. 4 is a control logic diagram for split loop injection modification of a low pressure coolant injector for a nuclear reactor facility.

[Explanation of symbols]

10 Reactor Building 20 Reactor 22 Drywell 24 Wetwell 26 Pressure Suppression Pool 37, 38 Fuel Storage Pool 102 Condensation Storage Tank 190 Safety Output (Initial Signal) 192 Low Water Level 194 High Drywell Pressure 200 Start of Diesel 202 Valves and Power available to pump motor and matched tolerance 208 Power on bus 210 Power on bus 214 Power on pumps 90, 91 218 Power on valves 120 and 124 222 Power on discharge valves 62 and 64 Allowance of 228 P1 or less Pressure 230 Allowable pressure below P2 234 Pump and valve actuation 236 Pump start 238 Inject valve open 240 Discharge valve closed 246 Pump for rated flow 254 Open injection valve 120, 124 256 Closed discharge 62 and 64

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Lawrence Li Chi 691, Los Pinos Place, Fremont, California, 94539, USA (72) Inventor Charles Henri Stall Pleasanton, USA, 94566, California , 514, Bonita Avenue (72) Inventor Galii Luis Sozui, 14970, Gelnail Avenue, Saratoga, CA, 95070, USA

Claims (20)

[Claims] 1. A core with normal operating pressure, first and second recirculation loops containing first and second circulation pumps and an operable discharge valve, respectively, a supplement pool water source, a condensation storage tank. , And a low pressure coolant injector for a nuclear facility of the type having a boiling water reactor with a safety device that produces a safety output in response to a loss of coolant accident. First and second low pressure coolant injection pumps operable for pumping; supply conduit means for connecting the suction inputs of the first and second low pressure coolant injection pumps in fluid flow communication with the suppression pool; The respective discharge outputs of the first and second low pressure coolant injection pumps and the respective first and second
First and second coolant injection conduits connected to the recirculation loop; one coolant injection conduit of the core for supplying a predetermined amount of water coolant to each of the first and second recirculation loops. First and second hydraulic pressures provided in the first and second coolant injection conduits for limiting the flow of the water coolant to a predetermined flow rate selected to be effective for performing emergency cooling. A low pressure coolant injection system for a nuclear facility, comprising: resistance means; and control means for operating the first and second low pressure coolant injection pumps in response to a safety output. 2. A first and second low pressure coolant injection valve operable in the first and second coolant injection conduits and between open and close directions; and the control means including the first in the open direction. And responsive to said safety output for simultaneously actuating a second low pressure coolant injection valve.
Low-pressure coolant injection device for a nuclear facility according to. 3. A predetermined pressure P1 presented by the boiling water reactor at which the control means is at or below the normal operating pressure.
A low pressure coolant injection system for a nuclear facility according to claim 2, responsive to actuate the low pressure coolant injection valve only in the presence of a. 4. The first and second hydraulic resistance means are first
A low pressure coolant injector for a nuclear facility according to claim 1 and comprising a second selectively shaped orifice. 5. The first and second coolant injection conduits are provided in the respective first between the reactor and the discharge valve.
And a second recirculation loop; and the control means is responsive to the safety output for actuating the discharge valves of the first and second recirculation loops to a closed condition. Low-pressure coolant injection device for a nuclear facility according to. 6. The first response second recirculation loop to the closed state only when the control means is in the presence of a predetermined pressure P2 exerted by the boiling water reactor at a value below the normal operating pressure. 6. The low pressure coolant injector for a nuclear facility according to claim 5, responsive to actuate the discharge valve of. 7. A first and second low pressure coolant injection valve in each of the first and second coolant injection conduits and operable between open and closed positions; and the control means includes the first and second coolant injection valves. 7. The low pressure coolant injection system for a nuclear facility according to claim 6, responsive to the safety output for simultaneously operating two low pressure coolant injection valves. 8. The control means is responsive to operate the low pressure coolant injection valve only in the presence of a predetermined pressure p1 exhibited by the boiling water reactor at a value below the normal operating pressure. The low pressure coolant injection device for a nuclear facility according to claim 7, wherein the predetermined pressure P1 is higher than the predetermined pressure P2. 9. The supply conduit means comprises the first and second supply conduits.
Cross tie conduit means for selectively interconnecting the discharge outputs of a low pressure coolant injection pump; said first by selecting said first and second coolant injection conduits
And cross tie valve means in the cross tie conduit operable between open and closed states to selectively direct the output of the first and second low pressure coolant injection pumps to one of the second recirculation loops; and The low pressure coolant injector for a nuclear facility according to claim 1, wherein the control means maintains the cross tie valve means in the open position in the presence of the safety output. 10. The nuclear facility of claim 1, wherein said supply conduit means connects said suction output of said first and second low pressure coolant injection pumps with said condensation storage tank. Low pressure coolant injection device. 11. An emergency core cooling water source, first and second independent recirculation loops for normally circulating water through the core for steam generation, and at least a predetermined amount of water coolant atoms responsive to a loss of coolant accident. In a low-pressure cooling water injection method for injecting low-pressure cooling water into a boiling water reactor of a nuclear facility having a safety device for generating a safety output for supplying to the reactor, each of And first and second water flow paths to the second recirculation loop; and low pressure coolant injection pumps operable to pump water from the water coolant source through the first and second water flow paths; Providing a valve device that can be actuated from a closed state to an open state to create a flow in the first and second water channels; a safety output to allow simultaneous flow of water coolant in the first and second water channels In response to the valve device A low pressure coolant injection pump is operated in response to the safety output; a flow of water coolant in the first and second water flow paths is cooled to the first and second independent recirculation loops by a predetermined amount of water. Low pressure, characterized in that it comprises a step of limiting to a predetermined fluid flow rate selected for supplying the material, said flow rate being selected so as to be effective in carrying out emergency cooling of the core from one water flow path. Cooling water injection method. 12. The step of limiting the flow of the water coolant in each of the first and second water flow paths is performed by applying a selective hydraulic resistance thereto. The low-pressure cooling water injection method according to the eleventh aspect. 13. The step of restricting the flow of the water coolant in each of the first and second water passages comprises providing selectively shaped orifices in each of the first and second water passages. The method according to claim 1, wherein
1. The low-pressure cooling water injection method described in 1. 14. The low pressure cooling of claim 11, wherein the steps of limiting the flow of the water coolant in each of the first and second water channels are performed simultaneously for each of the channels. Water injection method. 15. The step of providing a low pressure injection cooling pump comprises providing a first low pressure coolant injection pump in a first safety section having a first input for pumping water from the water source through the first water flow path; Providing a second low pressure coolant injection pump in a second safety section having a second output for pumping water from said water source through said second water flow path; and said said first and second low pressure coolant injection pumps, respectively. The low-pressure cooling water injection method according to claim 11, wherein the first and second outputs are jointly connected. 16. A cross tie valve is provided between the respective first and second low pressure coolant injection pumps and the first and second outputs; and the cross tie valve is opened in response to the safety output. The method of injecting low-pressure cooling water according to claim 15, further comprising the step of: 17. The first and second recirculation loops,
First and second recirculations each having an input side in fluid communication with the reactor from a position below the core and a discharge side in fluid communication with the reactor at a position above the core. A pump, and each of the first and second recirculation loops further includes a discharge valve disposed on the discharge side of each of the first and second recirculation pumps; and each of the discharge valves to the safety output. The low pressure cooling water injection method according to claim 11, further comprising a step of responding to the closing. 18. A boiling water reactor having a core and a normal operating pressure, first and second recirculation loops respectively including first and second recirculation pumps and an operable discharge valve, a suppression. In a low pressure coolant injector for a nuclear facility of the type having a pool water source, a condensation storage tank, and a safety device that produces a safety output in response to a loss of coolant accident, to have suction input and discharge output and to pump water. First and second low pressure coolant injection pumps operable;
Providing to connect the suction inputs of the first and second low pressure coolant injection pumps in fluid flow communication with the suppression pool, and further selectively discharging the discharge outputs of the first and second low pressure coolant injection pumps. Supply conduit means including a cross tie conduit arrangement connected to the first and second low pressure coolant injection pumps and respective first and second recirculation loops.
And a second coolant injection conduit; first and second low pressure conduit injection valves, respectively, provided within the first and second coolant injection conduits and operable between closed and open directions;
And first and second coolant injection conduits for limiting the flow of the water coolant to a predetermined fluid rate selected to supply a predetermined amount of water coolant to the second recirculation loop, respectively. A first and a second hydraulic resistance device within the cross tie conduit, the flow rate being selected to effectuate emergency cooling of the core from one coolant injection conduit; A cross tie operable between open and closed states for selectively directing the output of the first and second low pressure coolant injection pumps through the first and second coolant injection conduits to one of the first and second recirculation loops. Valve means; and said first and second low pressure coolant injection pumps in response to a safety output,
A low pressure coolant injection system for a nuclear facility, comprising control means for activating the first and second low pressure coolant injection valves and maintaining the cross tie valve system in the open position in the presence of a safety output. 19. The supply conduit means provides connection to the condensation storage tank and the suction output of the first and second low pressure coolant injection pumps.
8. A low pressure coolant injection device for a nuclear facility according to item 8. 20. Low pressure cooling for a nuclear facility according to claim 18, wherein said first and second hydraulic resistance means comprise first and second selectively shaped orifices. Material injection device.